The invention is related to the field of air bearing sliders for use in magnetic head assemblies.
In a computer disk drive, data is stored and retrieved by using one or more magnetic heads positioned close to a rotating disk containing magnetic material which records the information. The write head operates to write data onto the disk by aligning magnetic poles of the magnetic material. A read head reads data by sensing the alignment of these poles. Typically, these are combined in a read/write head containing both devices. Because the magnetic fields are very small, it is important that the read and/or write head is located very near the surface of the disk. The closer the head can be placed to the disk surface, the greater the storage capacity of the disk can be. Heads are typically mounted to air bearing sliders which are specifically shaped so that when placed into an air-stream existing close to the surface of a rotating disk, the movement of the disk relative to the slider will provide a lifting force to cause it to fly above the disk.
Magnetic heads are usually mounted to sliders either at a position near the center of the back end of the slider, or at the end of one or both of the side rails of the slider. The front end of the slider is typically higher than the rear end, which aids in establishing air flow into regions of positive pressure, which act to lift the slider. This also allows the heads to be positioned closer to the disk surface. The lower surface of the slider is generally known as the Air Bearing Surface (ABS), and the shape of this ABS is crucial to several different parameters which affect slider and head performance.
It is very important that the heads be maintained at a very precise and unvarying distance from the surface of the disk. Usually, the slider and magnetic head assembly is bonded to an actuator arm which allows the slider to maintain a desired position relative to the disk surface. The actuator arm also enables movement of the slider across the disk surface to precise positions over individual data tracks of the disk.
Generally, as the airflow is increased, the slider will produce greater lift and thus raise to a higher position above the disk surface. This causes the slider to vary its height as its location along the radius of the disk is changed. The closer to the center of the disk the slower the airflow, the lower the lift force and thus the lower the slider will fly. The closer to the outer edge the slider is, the faster the airflow, the greater the lift force and the higher the slider will fly. However, fluxuations in flying height are undesirable as a more constant flying height would allow the magnetic head to be positioned closer to the disk surface regardless of its radial location above the disk.
In order to maintain a more constant flying height, it has become the practice to contour the ABS so as to create regions of negative pressure, that is areas of sub-ambient pressure, which act to create a balancing xe2x80x9csuctionxe2x80x9d force which draws the slider downwards towards the disk surface. These are generally formed by creating cavities into which the air-streams can accelerate, thus causing a localized drop in pressure in these cavity areas. These negative pressure areas can serve to counter the forces generated by the positive pressure areas, and thus balance the forces at some equilibrium. Since the negative pressure forces can be expected to increase with increased air-flow, this is an effective way of countering the increase in positive pressure caused by increased air flow at the outer radius of the disk.
The use of negative pressure areas have several other advantages as well. Variations in the loading of the slider will also affect the flying height. The degree to which the flying height will be affected by variations in loading is referred to as load sensitivity. A slider which provides a lower load sensitivity is said to have high vertical stiffness. There can also be variations in air pressure, as for instance, when a slider is operated at high altitudes where the air is thinner and the positive pressure lifting force is decreased. This variation in performance with variations in altitude may be termed altitude sensitivity. A slider with high stiffness also generally produces less altitude sensitivity. The use of negative pressure zones in the ABS is an effective way of producing high stiffness, which is beneficial on both accounts.
In a typical alternate mode of operation, the read/write head is operated by a method known as Contact Start/Stop (CSS). In this method, the slider is parked in a landing zone near the inner diameter of the disk. The actuator arm moves the slider to this landing zone, and then the rotational speed of the disk slows gradually. The positive pressure at the ABS gradually decreases until the slider comes to rest, contacting the disk surface.
Recently, another mode of operation has been developed, called Load/Unload. In this mode, when the head is to be parked, as on start-up or power-down, the slider is carried by the actuator to the outer edge of the disk. There is a small ramp, up which the actuator arm is carried, and then the arm comes to rest a short distance above the disk surface. The slider thus never contacts the disk surface, and a certain amount of wear on the slider is thus avoided.
There have been certain problems with this mode of operation, however. The parked position of the arm is physically elevated about the level of the disk, so it is necessary to lift the arm, including the slider, from proximity with the disk. The slider is attached to the arm by a flexible suspension membrane, which, in order to minimize weight and provide flexibility, is made to be very thin. In sliders with an ABS which uses negative pressure areas to maintain a constant fly height, the negative pressure naturally opposes the lifting of the slider from the disk surface. If the membrane is fragile enough, or if the negative pressure force is great enough, the membrane can be torn or damaged as the slider is pulled away from the disk surface.
Thus there is a need for a slider having an air-bearing surface including negative pressure areas for stability, but which is more easily disengaged from proximity to the disk surface without risk of damage to actuator-arm components.
The slider of the present invention is configured to be used with load/unload drives, and to aid in disengagement from the disk surface during unload operations. The slider includes sub-ambient, or negative pressure zones having a pressure center which is located towards the trailing edge of the slider compared to the load point. This allows the creation of a moment about the load point which acts to create a rotation about the load point. This rotation tends to lift the leading edge away from the disk surface. More air is then funneled into the gap between the air bearing surface and the disk surface. The surface of the negative pressure cavity or cavities is also brought away from the disk surface disrupting the negative pressure and releasing the slider from engagement with the disk surface. Once the negative pressure has been disrupted, the force opposing the lifting of the arm is reduced or dispelled, and the arm can be lifted into the load/unload ramp without damage to the actuator arm or its components.
Accordingly, it is an object of the present invention to provide a slider which has high stiffness, and thus good flying height stability, low load sensitivity, and low altitude sensitivity.
Another object of the invention is to provide a slider which can be used with load/unload disk drive operations.
And another object of the invention is to provide a slider which can be disengaged from the disk surface without causing damage to the actuator arm suspension membrane.
Briefly, one preferred embodiment of the present invention is a disk drive having an actuator arm, a slider and a suspension membrane which attaches the slider to the actuator arm. The slider includes a leading edge, a trailing edge, a number of pads and a cavity, which creates a region of sub-ambient pressure, including a negative pressure center. A load point is formed where the suspension membrane attaches to the slider. The negative pressure center is positioned towards the trailing edge relative to the load point, such that when upward force is applied to the slider at the load point, a moment is produced which raises the leading edge, allowing increased air flow into the cavity, which diminishes the sub-ambient pressure, and allows the arm to be raised without damaging the suspension membrane.
An advantage of the present invention is that the slider of the present invention has a very low standard deviation in flying height.
Another advantage of the invention is that the slider of the present invention has very low load sensitivity.
And another advantage of the invention is that the slider of the present invention has very low altitude sensitivity.
A further advantage of the present invention is that the slider produces a relatively large negative pressure force, and a comparatively small unload force.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the several figures of the drawings.